Junkyard Musings and Questions...

[Gary Lewis]

I don't know, Gary. I once thought so and thought about mounting a gauge, there.

I believe Jonathan will have a definitive answer.

Hopefully I will answer everyone’s questions...

The cluster itself will interchange (white shell is the same). The circuit films are the same, even the ones with electric speedometer. The 1980 medium duty have the green film and different indicator light pinning just like the light pickups.

The later medium duty had an electronic 75 mph speedometer. I don’t know if there is a way to make this work with a tone ring rear end, but that might be a project for someone who is good with electronics.

The trim piece below the steering column does not fit our trucks. The column axis is slightly shifted and the opening is longer on the Medium duty trucks. Trent is modifying one to fit, but it requires cutting and gluing plastic, fabricating a mount for the cable pull plate etc., it’s anything but a direct bolt-in, and generally too small for gauges.

Jonathan - Thanks. So, that's what Trent is doing - including one for me he said. And, while it may be too small for gauges, I want one for a switch or switches. One for the PTO function feeding to the EEC-V system to up the idle speed on Big Blue, both for alternator output while winching as well as for compressed air output while airing up. So a switch and an indicator, bright enough to get your attention, would be great.

Cory - I'd still like to have it, as well as the bracket behind it if reasonably possible. But, there's absolutely no hurry.

[Rembrant]

I don't know, Gary. I once thought so and thought about mounting a gauge, there.

I believe Jonathan will have a definitive answer.

Hopefully I will answer everyone’s questions...

The cluster itself will interchange (white shell is the same). The circuit films are the same, even the ones with electric speedometer. The 1980 medium duty have the green film and different indicator light pinning just like the light pickups.

The later medium duty had an electronic 75 mph speedometer. I don’t know if there is a way to make this work with a tone ring rear end, but that might be a project for someone who is good with electronics.

The trim piece below the steering column does not fit our trucks. The column axis is slightly shifted and the opening is longer on the Medium duty trucks. Trent is modifying one to fit, but it requires cutting and gluing plastic, fabricating a mount for the cable pull plate etc., it’s anything but a direct bolt-in, and generally too small for gauges.

Hey Jon

What about the 3500 rpm diesel tach pictured? Will it work in the bullnose trucks?

[Ford F834]

Jonathan - Thanks. So, that's what Trent is doing - including one for me he said. And, while it may be too small for gauges, I want one for a switch or switches. One for the PTO function feeding to the EEC-V system to up the idle speed on Big Blue, both for alternator output while winching as well as for compressed air output while airing up. So a switch and an indicator, bright enough to get your attention, would be great.

Cory - I'd still like to have it, as well as the bracket behind it if reasonably possible. But, there's absolutely no hurry.

Cory, I forgot to mention that the 4,500 gas tach is extremely desirable for us straight six guys. David and I are both running them, but I believe Dave/FuzFace is looking for one if you can get it. The 3,500 diesel tach is pretty specific to the truck as it reads flywheel teeth. I have not messed with the one David gave me, but I don’t think there is any easy way to make it work on our engines.

Other desirable things to look for on the medium duty trucks are the aluminum grab handles by the doors (get the stainless torx fasteners and plastic wedges with it), the west coast type mirrors fetch a pretty penny, and of course the center/radio bezel if it’s any good. The black weave with “FORD” script in the nameplate area is nice...

[Rembrant]

Cory, I forgot to mention that the 4,500 gas tach is extremely desirable for us straight six guys. David and I are both running them, but I believe Dave/FuzFace is looking for one if you can get it.

OK, good to know on the diesel tach. I won't waste any time on it. The radio bezels were damaged in every truck I looked at, so not much there worth taking. I'll grab the cluster with the 4500 RPM gas tach. I'm looking at buying a 300/6 truck myself with no tach, so I was going to grab it anyway...and if I end up having no use for it, I'll pass it along to somebody else.

Thanks for the info Jon.

 

[Ford F834]

Hey Jon

What about the 3500 rpm diesel tach pictured? Will it work in the bullnose trucks?

When I get my diesel running I’m going to plug in the 3,500 rpm tach just to see if it reads with the IP gear signal. My hunch is that it will read, but that it will be off. The IP gear has 106 teeth, and turns once for every two crankshaft revolutions. The sensor generates 53 pulses per revolution. I think I was told the 3,500 tachs read a 126 tooth flywheel. You could probably build a 126 tooth star wheel and mount an ABS wheel sensor to generate the signal, but you would have to really want it.

[Ford F834]

Cory, I forgot to mention that the 4,500 gas tach is extremely desirable for us straight six guys. David and I are both running them, but I believe Dave/FuzFace is looking for one if you can get it.

OK, good to know on the diesel tach. I won't waste any time on it. The radio bezels were damaged in every truck I looked at, so not much there worth taking. I'll grab the cluster with the 4500 RPM gas tach. I'm looking at buying a 300/6 truck myself with no tach, so I was going to grab it anyway...and if I end up having no use for it, I'll pass it along to somebody else.

Thanks for the info Jon.

If you go to use the 4,500 gas tach on a straight six, they are wired differently on the printed circuit board. To get it to read right you have to isolate the lug on the back that says “8”. Then it will read correctly 👍

 

[Steve83]

...electronic 75 mph speedometer. I don’t know if there is a way to make this work with a tone ring rear end...

Do you know what that speedo was designed to read? A sensor on the speedo cable?

To get it to read right you have to isolate the lug on the back that says “8”. Then it will read correctly

That's usually built into the engine or dash harness, depending on year.

[Ford F834]

...electronic 75 mph speedometer. I don’t know if there is a way to make this work with a tone ring rear end...

Do you know what that speedo was designed to read? A sensor on the speedo cable?

To get it to read right you have to isolate the lug on the back that says “8”. Then it will read correctly

That's usually built into the engine or dash harness, depending on year.

Steve, unfortunately I have no idea where the speed signal came from on the late medium duty trucks. It would be nice to find out... and if I find one in the junkyard I will investigate.

You are right regarding the grounding in the truck harness for 6 vs 8 cylinders... however the medium duty 4,500 rpm gas tach was only engineered for 8 cylinder applications. The printed circuit inside the tach itself is only configured for 8 cylinder truck harnesses. When installed on a 6 cylinder truck the way it is grounded causes it to read incorrectly (too high). Isolating the “8” terminal corrects the problem. I can’t really explain how that happens, but once I isolated that lug the tach was very close to what my tach/dwell meter was reading at the coil.

[1986F150Six]

Steve, unfortunately I have no idea where the speed signal came from on the late medium duty trucks. It would be nice to find out... and if I find one in the junkyard I will investigate.

You are right regarding the grounding in the truck harness for 6 vs 8 cylinders... however the medium duty 4,500 rpm gas tach was only engineered for 8 cylinder applications. The printed circuit inside the tach itself is only configured for 8 cylinder truck harnesses. When installed on a 6 cylinder truck the way it is grounded causes it to read incorrectly (too high). Isolating the “8” terminal corrects the problem. I can’t really explain how that happens, but once I isolated that lug the tach was very close to what my tach/dwell meter was reading at the coil.

With Jonathan's input, I isolated the "8" lug by wrapping it with Teflon tape and installing a small [plumbing] rubber washer, before tightening the "nut". The printed circuit does not actually touch the lug... it is the "nut" that makes the connection.

[Rembrant]

With Jonathan's input, I isolated the "8" lug by wrapping it with Teflon tape and installing a small [plumbing] rubber washer, before tightening the "nut". The printed circuit does not actually touch the lug... it is the "nut" that makes the connection.

That’s great thanks David!

That answered my next question!